Oil-based drilling fluid and preparation method thereof

Abstract

The present invention relates to the technical field of oil and gas field drilling, and in particular to an oil-based drilling fluid and a preparation method thereof. It is composed of the following substances by weight: 100 parts of base oil, 20-30 parts of CaCl2 aqueous solution with a concentration of 25%, 0.5-1.5 parts of primary emulsifier, 2-5 parts of auxiliary emulsifier, 1-3 parts of wetting agent, 2-7 parts of fluid loss reducer, 1-3 parts of organic soil, 10-20 parts of barite, and 1-10 parts of plugging agent; the plugging agent is selected from one of ZIF‑8@rGO microsphere plugging agent, ZIF‑7@rGO microsphere plugging agent and ZIF‑11@rGO ​​microsphere plugging agent. The raw materials of the present invention are simple, the economic benefits of drilling operations are improved, and it can be used in a variety of drilling environments, including high temperature, high pressure and high salinity conditions, which improves the scope of application of the drilling fluid. The ZIF‑8@rGO microsphere plugging agents, ZIF‑7@rGO microsphere plugging agents and ZIF‑11@rGO ​​microsphere plugging agents used can significantly reduce the permeability of artificial cores.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field drilling, and in particular to an oil-based drilling fluid and a preparation method thereof. Background Art

[0002] The performance of water-based drilling fluid is usually improved through a variety of methods, such as controlling the hydration of shale, increasing the viscosity and shear force of the drilling fluid, and using plugging materials. These additives are mainly polymers, but they are prone to failure in high-temperature bottom hole environments, resulting in a decrease in the performance of the drilling fluid. In addition, water-based drilling fluid is mainly used for vertical drilling. In horizontal drilling or long horizontal section drilling, the larger contact area with the well wall will increase friction, thereby significantly reducing the drilling speed. At the same time, the penetration of the water phase may also destroy the shale structure and increase the risk of well wall instability or even collapse.

[0003] Compared with water-based drilling fluid, oil-based drilling fluid has better lubricity, inhibition and high temperature resistance, so it is often used in horizontal drilling. However, oil-based drilling fluid may cause wellbore instability due to the penetration of oil phase during drilling, causing complex situations downhole.

[0004] In order to reduce the instability of the wellbore in horizontal drilling, plugging agents specially added to oil-based drilling fluids can be used to seal tiny pores and cracks to prevent or reduce the penetration of liquid into the reservoir, reduce changes in the microstructure of the reservoir rock, and reduce filtration. Currently, commonly used plugging agents include nano-silicon dioxide, nano-calcium carbonate, and polymer nanomaterials. Summary of the invention

[0005] The object of the present invention is to provide a new oil-based drilling fluid and a preparation method thereof based on the prior art.

[0006] The present invention is achieved through the following technical solutions:

[0007] An oil-based drilling fluid is composed of the following substances in parts by weight: 100 parts of base oil, 20-30 parts of a 25% CaCl2 aqueous solution, 0.5-1.5 parts of a primary emulsifier, 2-5 parts of an auxiliary emulsifier, 1-3 parts of a wetting agent, 2-7 parts of a filtrate reducer, 1-3 parts of organic soil, 10-20 parts of barite, and 1-10 parts of a plugging agent; the plugging agent is selected from one of a ZIF-8@rGO microsphere plugging agent, a ZIF-7@rGO microsphere plugging agent, and a ZIF-11@rGO ​​microsphere plugging agent.

[0008] Based on their special nano-micron quasi-one-dimensional physical structure and strong surface lipophilicity, ZIF-8@rGO microsphere plugging agent, ZIF-7@rGO microsphere plugging agent and ZIF-11@rGO ​​microsphere plugging agent not only ensure their dispersibility in the oil phase, but also can effectively plug the nano-micron pores of the rock sample. The base oil is selected from one of 3# white oil or 0# diesel, preferably 3# white oil.

[0009] The present invention also provides a method for preparing an oil-based drilling fluid, comprising the following steps: adding a primary emulsifier, a CaCl2 aqueous solution and an auxiliary emulsifier to the base oil, stirring at a high speed of 10000 rpm for 10 minutes, maintaining the stirring speed, then adding a wetting agent and a filtration reducer, continuing stirring for 10 minutes, then adding organic soil, barite and a plugging agent, and continuing stirring for 20 minutes.

[0010] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0011] The invention has simple raw materials, improves the economic benefits of drilling operations, can be used in a variety of drilling environments, including high temperature, high pressure and high salinity conditions, and improves the application range of drilling fluids. The ZIF-8@rGO microsphere plugging agent, ZIF-7@rGO microsphere plugging agent and ZIF-11@rGO ​​microsphere plugging agent used can significantly reduce the permeability of artificial cores. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0013] All chemical reagents in the present invention are analytically pure and purchased from commercial products. GO is graphene oxide, rGO is reduced graphene oxide. 25% CaCl2 aqueous solution in the present invention is a mass ratio, and white oil is 3# white oil.

[0014] The preparation method of the ZIF-8@rGO microsphere plugging agent in the present invention is:

[0015] 150 mg of GO was added to 100 mL of deionized water and ultrasonicated for 8 h. Then 0.117 g of Zn(NO3)2·6H2O and 2.27 g of 2-methylimidazole were added. The mixture was stirred at room temperature of 25 °C for 0.5 h. After centrifugation and precipitation, the mixture was washed with deionized water three times and vacuum dried to obtain ZIF-8@rGO nanosheets.

[0016] Take 0.5g ZIF-8@rGO and disperse it in 20mL deionized water, add 1.0g L-ascorbic acid, and after the L-ascorbic acid is evenly dissolved, add it into methyl silicone oil preheated to 160°C at a rate of 0.5mL / min and continue stirring. After the addition is completed, continue to react in methyl silicone oil at 160°C for 0.5h, then cool naturally to room temperature, centrifuge to obtain a precipitate, wash the precipitate with n-heptane, and after washing, dry the precipitate under vacuum at 200°C to obtain ZIF-8@rGO microspheres.

[0017] The preparation method of the ZIF-8@rGO nanosheet plugging agent in the present invention is:

[0018] 150 mg of GO was added to 100 mL of deionized water and ultrasonicated for 8 h. Then 0.117 g of Zn(NO3)2·6H2O and 2.27 g of 2-methylimidazole were added. The mixture was stirred at room temperature of 25 °C for 0.5 h. After centrifugal precipitation, the mixture was washed three times with deionized water and vacuum dried to obtain ZIF-8@rGO nanosheets.

[0019] The preparation method of the ZIF-7@rGO microsphere plugging agent in the present invention is:

[0020] 0.423 g Zn(NO3)2·6H2O and 10.77 g benzimidazole were dissolved in 140 mL DMF, stirred at room temperature of 25 °C for 24 h, centrifuged, and the precipitate was washed three times with methanol and dried at 80 °C in vacuum for 12 h to obtain ZIF-7@rGO nanosheets;

[0021] Take 0.5g ZIF-7@rGO nanosheets and disperse them in 20mL deionized water. Add 1.0g L-ascorbic acid. After the L-ascorbic acid is evenly dissolved, add it into methyl silicone oil preheated to 160°C at a rate of 0.5mL / min and continue stirring. After the addition is completed, continue to react in methyl silicone oil at 160°C for 0.5h. Then, cool naturally to room temperature, centrifuge to obtain a precipitate, wash the precipitate with n-heptane, and after washing, dry the precipitate under vacuum at 200°C to obtain ZIF-7@rGO microspheres.

[0022] The preparation method of the ZIF-11@rGO ​​microsphere plugging agent in the present invention is:

[0023] 0.24 g of benzimidazole was weighed and dissolved in 5 mL of methanol, and then 8 mL of toluene and 2.4 g of ammonia water were added; 0.22 g of Zn(CH3COO)2·2H2O was dissolved in 2.5 mL of methanol; the two solutions were mixed together and stirred at room temperature of 25°C for 10 min, centrifuged to obtain a precipitate, washed with methanol three times and then vacuum dried at 80°C for 12 h to obtain ZIF-11@rGO ​​nanosheets;

[0024] Take 0.5g ZIF-11@rGO ​​nanosheets and disperse them in 20mL deionized water. Add 1.0g L-ascorbic acid. After the L-ascorbic acid is evenly dissolved, add it into methyl silicone oil preheated to 160°C at a rate of 0.5mL / min and continue stirring. After the addition is completed, continue to react in methyl silicone oil at 160°C for 0.5h. Then, cool naturally to room temperature, centrifuge to obtain a precipitate, wash the precipitate with n-heptane, and after washing, dry the precipitate under vacuum at 200°C to obtain ZIF-11@rGO ​​microspheres.

[0025] Example 1

[0026] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 1 part of a ZIF-8@rGO microsphere plugging agent.

[0027] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0028] Example 2

[0029] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 2 parts of a ZIF-8@rGO microsphere plugging agent.

[0030] Oil-based drilling fluid, the drilling fluid preparation method is to add the main emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to the white oil, stir at a high speed of 10000rpm for 10min, maintain the stirring speed, then add the wetting agent and the filtration reducer, continue to stir for 10min, then add the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continue to stir for 20min.

[0031] Example 3

[0032] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 3 parts of a ZIF-8@rGO microsphere plugging agent.

[0033] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0034] Example 4

[0035] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 4 parts of a ZIF-8@rGO microsphere plugging agent.

[0036] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0037] Example 5

[0038] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a fluid loss reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 5 parts of a ZIF-8@rGO microsphere plugging agent.

[0039] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0040] Example 6

[0041] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 8 parts of a ZIF-8@rGO microsphere plugging agent.

[0042] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0043] Example 7

[0044] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 10 parts of a ZIF-8@rGO microsphere plugging agent.

[0045] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0046] Comparative Example 1

[0047] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a fluid loss reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 8 parts of a ZIF-8@rGO nanosheet plugging agent.

[0048] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-8@rGO nanosheet plugging agent, and continuing to stir for 20 min.

[0049] Comparative Example 2

[0050] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 8 parts of a ZIF-7@rGO microsphere plugging agent.

[0051] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-7@rGO microsphere plugging agent, and continuing to stir for 20 min.

[0052] Comparative Example 3

[0053] An oil-based drilling fluid consists of the following substances in parts by weight: 100 parts of white oil, 25 parts of a 25% CaCl2 aqueous solution, 1 part of a primary emulsifier oleic acid, 3 parts of an auxiliary emulsifier Span-80, 1.3 parts of a wetting agent dodecyltrimethylammonium bromide, 5 parts of a filtrate reducer humic acid, 2 parts of organic soil, 15 parts of barite, and 8 parts of a ZIF-11@rGO ​​microsphere plugging agent.

[0054] The preparation method of oil-based drilling fluid is as follows: after adding the primary emulsifier, CaCl2 aqueous solution and auxiliary emulsifier to white oil, stirring at a high speed of 10000 rpm for 10 min, maintaining the stirring speed, then adding the wetting agent and the filtration reducer, continuing to stir for 10 min, and then adding the organic soil, barite and ZIF-11@rGO ​​microsphere plugging agent, and continuing to stir for 20 min.

[0055] Test Example 1

[0056] Drilling fluid plugging performance test.

[0057] Artificial cores are used to simulate nano- and micro-pore formations. The average flow rate of the drilling fluid system in the artificial cores is measured, and the permeability K = Qμl / (AΔP) of the artificial cores before and after the plugging agent is added is calculated using the Darcy formula.

[0058] The plugging rate is (initial permeability - permeability after plugging) / initial permeability × 100%.

[0059] The permeability of the artificial core without adding any plugging material refers to the permeability of the artificial core without adding the ZIF-8@rGO microsphere plugging agent on the basis of Example 1.

[0060] Table 1. Permeability performance test

[0061]

[0062] It can be seen from the data in Table 1 that the use of ZIF-8@rGO microsphere plugging agent can effectively reduce the permeability of the artificial core. As the content of ZIF-8@rGO microsphere plugging agent increases, the permeability gradually decreases. In Example 6, that is, 8 parts, the best effect is achieved. If the content is continued to be added, the effect is not obvious. When the addition amount of ZIF-7@rGO microsphere plugging agent and ZIF-11@rGO ​​microsphere plugging agent is 8 parts, the permeability is not as good as that of ZIF-8@rGO microsphere plugging agent.

[0063] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. An oil-based drilling fluid, characterized in that: The composition is composed of the following materials by weight: 100 parts of base oil, 20-30 parts of 25% CaCl2 aqueous solution, 0.5-1.5 parts of primary emulsifier, 2-5 parts of auxiliary emulsifier, 1-3 parts of wetting agent, 2-7 parts of fluid loss reducer, 1-3 parts of organic soil, 10-20 parts of barite, and 1-10 parts of plugging agent; The plugging agent is selected from ZIF-8@rGO microsphere plugging agent; The preparation method of the ZIF-8@rGO microsphere plugging agent is as follows: 150 mg of GO was added to 100 mL of deionized water and ultrasonicated for 8 h. Then 0.117 g of Zn(NO3)2·6H2O and 2.27 g of 2-methylimidazole were added. The mixture was stirred at room temperature of 25 °C for 0.5 h. After centrifugation and precipitation, the mixture was washed with deionized water three times and vacuum dried to obtain ZIF-8@rGO nanosheets. Take 0.5g ZIF-8@rGO and disperse it in 20mL deionized water, add 1.0g L-ascorbic acid, and after the L-ascorbic acid is evenly dissolved, add it into methyl silicone oil preheated to 160°C at a rate of 0.5mL / min and continue stirring. After the addition is completed, continue to react in methyl silicone oil at 160°C for 0.5h, then cool naturally to room temperature, centrifuge to obtain a precipitate, wash the precipitate with n-heptane, and after washing, dry the precipitate under vacuum at 200°C to obtain ZIF-8@rGO microspheres.

2. The oil-based drilling fluid according to claim 1, characterized in that: The base oil is selected from one of 3# white oil and 0# diesel.

3. The oil-based drilling fluid according to claim 2, characterized in that: The base oil is selected from 3# white oil.

4. The oil-based drilling fluid according to claim 1, characterized in that: The fluid loss reducer is at least one of sodium carboxymethyl cellulose or humic acid.

5. The oil-based drilling fluid according to claim 1, characterized in that: The base oil is selected from 3# white oil, the primary emulsifier is selected from oleic acid, and the auxiliary emulsifier is selected from Span-80.

6. The oil-based drilling fluid according to claim 5, characterized in that: The wetting agent is selected from dodecyltrimethylammonium bromide, and the fluid loss reducer is selected from humic acid.

7. The method for preparing an oil-based drilling fluid according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding a primary emulsifier, a CaCl2 aqueous solution and an auxiliary emulsifier to the base oil, stirring at a high speed of 10000 rpm for 10 minutes, maintaining the stirring speed, then adding a wetting agent and a filtration reducer, continuing stirring for 10 minutes, then adding organic soil, barite and a plugging agent, and continuing stirring for 20 minutes.

Images